Corn steep liquor (CSL), a byproduct of the corn wet milling process, is used as an additive to improve the quality of compost and could be used as a fertilizer. At the Spring 2011 board meeting, the NOSB will vote to determine whether CSL is considered synthetic (and therefore prohibited, unless exempted on the National List) or nonsynthetic (allowed, unless prohibited on the National List). (See NOSB's definition of synthetic substances.)
In the past, CSL has been considered nonsynthetic by stakeholders, but was more recently classified as synthetic by the Organic Materials Review Institute (OMRI), using the NOSB’s 2005 clarifications regarding the classification of synthetic and nonsynthetic substances. In April 2010, the NOP requested that the NOSB review the process for CSL concerning its classification as synthetic or nonsynthetic as an input for crop production for the October 2010 NOSB meeting. The NOSB Crops Committee (CC) asked for an analysis of relevant issues by the USDA Agricultural Marketing Service (AMS) Science and Technology Program (S&T).
In a nutshell, the question comes down to the addition of sulfur dioxide (SO2) in the milling process. If SO2 cleaves disulfide bonds making amino acids available for plant uptake, then chemical change has occurred and CSL is synthetic. If the SO2 merely acts to prevent putrification, and the disulfide bonds are broken naturally during lactic acid fermentation, then CSL would be considered nonsynthetic. Based on information provided by S&T, the CC voted that CSL is synthetic, but there was a strong minority opinion that it is nonsynthetic. A full NOSB vote on was tabled at the October 2010 meeting and is expected to be voted upon at the April 2011 meeting.
Read the NOSB Crops Committee's Corn Steep Liquor synthetic/nonsynthetic determination (September 9, 2010)